Electric key switching unit



N. E. BERG ELECTRIC KEY SWITCHING UNIT Filed Sept. 6, 1968 United States Patent 3,533,028 ELECTRIC KEY SWITCHING UNIT Nephi Edward Berg, Bedford, N.H., assignor, by mesne assignments, to Hendrix Electronics Inc., Milford, N.H., a corporation of Delaware Filed Sept. 6, 1968, Ser. No. 757,997 Int. Cl. H0111 51/28 US. Cl. 335-205 Claims ABSTRACT OF THE DISCLOSURE A key operated switching unit has a magnetic reed switch capsule whose contacts are closed by movement of a permanent magnet. The capsule is cemented in a channel molded in a plastic block. The magnet is cemented in a recess on a spring-urged carrier sliding in a parallel channel. A key piece is fixed to the end of a shank on the carrier which extends out of the block through a cap.

A known form of switch unit or module comprising a housing for a sliding carirer of a permanent magnet and a glass capsule enclosing reed contacts of conductive and magnetic material which are opened or closed by moving the carrier and magnet to a position in which the magnetic field pulls the contacts together. Such units as are shown in US. Pat. Nos. 3,223,801 and 3,283,274, for example, provide compact, trouble-free switches, useful in various applications. Such prior switching modules have, however, a complex and expensive design and are unsuitable for use in large numbers. On a typewriter keyboard, for example, requiring several dozen such switching units, the expense and manufacturing time of prior units make them impractical.

The object of the present invention is to provide a greatly simplified switching unit which has a minimum of parts, is economical of material, and is quickly and easily assembled.

According to the invention an electric key switching unit comprises a body of non-magnetic material having a straight channel therein, a carrier slidable longitudinally in the channel, a magnet on the carrier, a switch fixed adjacent the channel with magnetically operated contacts closing in response to movement of the carrier and magnet between two positions, and spring means yieldingly urging the carrier to one of said positions, characterized by a shank of reduced transverse dimension molded integrally with the carrier, and extending out of the channel, a cap piece fixed to one end of said body and having an opening therethrough from said channel receiving said shank and forming a stop for one position of the carrier, and a key piece fitted over said shank for manual actuation of the carrier.

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawing in which:

FIG. 1 is an elevation of a key switching module;

FIG. 2 is an enlarged section on line 22 of FIG. 1;

FIG. 3 is a section on line 33 of FIG. 1;

FIG. 4 is a bottom view of the module; and

FIG. 5 is an exploded isometric view.

As shown in the drawing a key switching unit comprises a rectangular block 1 of injection molding plastic such as nylon or Lucite which are both insulative and non-magnetic. A carrier 2 of like material and having an integral shank 3 of reduced transverse dimension slides longitudinally in a first rectangular channel 4 molded in the block. Transversely of its sliding movement the carrier 2 conforms to the cross-section of the channel 4. Cemented in a recess 6 through the carrier is a permanent magnet 7 3,533,028 Patented Oct. 6, 1970 'ice having its poles N and S oriented longitudinally of the sliding movement of the carrier. While the magnet is cemented in the recess 6 for convenience of assembly, the magnet is also confined between the walls of the carrier channel 4 and is held in position in the failure or absence of cement. Molded parallel to the rectangular channel 4 is a second straight channel 8 in which is pressed-fitted or cemented a glass capsule 9 containing magnetic reed contacts 11. The lead 12 from the upper contact runs upwardly through the channel 8, thence along a recess 13 in the top of the block 1, and down through a passage 14 out of the bottom of the block. The lead 16 from the lower contact runs out of the bottom of the block 1 through a passage 17. Because of the insulative character of the block and the separation of the passages 14 and 17, the leads 12 and 16 need no insulating cover.

The shank 3 of the carrier 2 extends out of the block 1 through an opening 21 in a plastic cap piece 22 cemented to the top of the block. The top face of the block has a stud 23 entering a hole 24 on the cap piece, and a like stud (not shown) on the cap piece enters a hole 26 in the block, to register the cap piece opening 21 with the rectangular carrier channel in the block. Formed between the main body of the carrier 2 and the shank 3 are shoulders 5 which abut the underside of the cap piece and stop the carrier in the upper position shown in FIG. 2.

A plastic finger key piece 27 has an integral socket 28 fitting over and cemented to a further reduced top portion 29 of the carrier shank 3. Between the underface of the key piece and the cap piece a coiled spring 28 is confined to urge the key and carrier to the upper position shown.

When the key 27 is depressed manually the south pole S of the magnet 7 slides downwardly with the carrier 2 to the position S opposite the magnetic contacts 11, drawing the contacts together and closing the switch.

As can be seen from the description the four partsblock 1, carrier 2, cap piece 22 and key piece 27are formed by simple injection molding of a plastic. Of the remaining parts, the reed switch 9 and magnet 7 are easily fitted or cemented into position without any further machining or tool operation. Then the cap piece 22 and key piece are cemented respectively to the block 1 and carrier shank 3 with the spring simply fitted on the shank. Thus the manufacture of the complete switch module consists of molding a minimum number of parts and fitting or cementing two plastic parts together after fitting or assembling the necessary magnet and switch capsule in place.

While one desirable embodiment of the invention has herein been disclosed by way of example, it is to be understood that the invention is broadly inclusive of any and all modifications falling within the terms of the appended claims.

I claim:

1. An electric key switching unit comprising:

a body of non-magnetic material having a slot therein,

a flat carrier slidable longitudinally in said slot, a magnet on the carrier, a switch fixed adjacent said slot with magnetically operated contacts closing in response to movement of the carrier and magnet between two positions, spring means yieldingly urging the carirer to one of said positions,

a shank of reduced transverse dimension formed integrally with the carrier, and extending out of said slot,

a cap piece fixed to one end of said body and having an opening therethrough from said slot receiving said shank and forming a stop for one position of the carrier, and

a key piece fitted over said shank for manual actuation of the carrier.

2. A unit according to claim 1 wherein said spring means comprises a coil surrounding and held on the shank, and confined between said cap piece and key piece.

3. A unit according to claim 1 wherein said switch is fixed in a channel molded within the body parallel to said slot.

'4. An electric key switching unit according to claim 1 wherein said magnet is confined in a recess in said carrier by the walls of said slot.

5. An electric key switching unit according to claim 1 wherein said stop comprises a shoulder on the carrier adjacent the shank, said spring means comprises a coil sur- 10 rounding and held on the shank, and confined between said cap piece and key piece, said switch is fixed in a References Cited UNITED STATES PATENTS 3,292,123 12/ 1966 Siklos 335-205 5,351,817 11/1967 Wadolny et al. 335-206 BERNARD A. GILHEANY, Primary Examiner R. N. ENVALL JR., Assistant Examiner 

